The single-centre, assessor-blinded study enrolled adults aged 18 to 55 years who had lived with upper trapezius myofascial pain syndrome for at least three months and had a baseline Visual Analog Scale (VAS) pain score of 4 or higher. Of 83 people screened, 66 were randomized, with 33 assigned to each protocol. The trial was designed to compare the effects of two stimulation durations rather than test rPMS against a no-treatment control.

Participants received either a 15-minute or 10-minute rPMS session once a week for four weeks. Both groups also completed standardized stretching exercises. Assessments were conducted at baseline, week 2 and week 4 by an assessor blinded to group assignment. The primary outcome was pain intensity measured with the VAS, while pressure pain threshold and the Neck Disability Index were secondary outcomes.

Linear mixed-effects models showed significant changes over time in all three outcomes across the trial, with p-values below 0.001. The models included group, time and group-by-time interaction terms, and analyses followed the intention-to-treat principle. Despite the marked improvements, the group-by-time interactions did not show significant differences between the 10-minute and 15-minute protocols.

At week 4, the reported average reduction in VAS score from baseline was 4.87 points for Protocol A and 5.02 points for Protocol B. The adjusted between-group difference was −0.27 points, with a 95% confidence interval of −0.95 to 0.40 and p = 0.43. Because the confidence interval included zero and values in both directions, the analysis did not identify one stimulation duration as superior for pain intensity.

Pressure pain threshold also improved across the two groups, rising by an average of 2.51 kg/cm². The adjusted between-group difference at week 4 was 0.17 kg/cm², with a 95% confidence interval of −0.70 to 1.03 and p = 0.71. For the Neck Disability Index, the average decline across the groups was 9.15 points. Its adjusted between-group difference was −0.64 points, with a 95% confidence interval of −3.29 to 2.02 and p = 0.64. Neither secondary outcome showed a statistically significant difference between protocols.

These findings indicate that both treatment groups improved during the four-week intervention and that extending the weekly rPMS session from 10 to 15 minutes did not produce a detected advantage in the measured outcomes. The result supports the shorter protocol as a possible practical option in rehabilitation settings, but it should not be interpreted as proof that the approaches are interchangeable. The confidence intervals for the treatment comparisons were compatible with modest differences in either direction.

The trial’s scope also limits the conclusions. Follow-up was limited to the four-week treatment period, so the study does not establish how long the observed improvements persisted or whether the protocols differ in longer-term outcomes. Because both groups received standardized stretching, the reported changes cannot be isolated to rPMS alone. Within this sample and follow-up period, however, the central result was consistent across pain intensity, pressure pain threshold and neck disability: no significant difference was detected between 10 and 15 minutes of weekly stimulation.

Subject of Research: Short-term comparison of 10- and 15-minute repetitive peripheral magnetic stimulation for upper trapezius myofascial pain syndrome

Article Title: Comparison of two repetitive peripheral magnetic stimulation protocols for upper trapezius myofascial pain syndrome: A randomized trial

Article References: Jongutchariya, T., Hangsaphruek, S., Wongkiratimethawi, T., & Saengsuwan, J. (2026). Comparison of two repetitive peripheral magnetic stimulation protocols for upper trapezius myofascial pain syndrome: A randomized trial. PLOS One, 21(10), e0360355. https://doi.org/10.1371/journal.pone.0360355

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360355

Keywords: randomized trial, repetitive peripheral magnetic stimulation, myofascial pain syndrome, neck pain, pain intensity, pressure pain threshold, neck disability, rehabilitation, treatment duration, Comparison, repetitive, peripheral